Over the past three decades there has been vast research and academic development in millimeter wave (mmWave) technology, which has corresponded to the steady growth in customer demand for mmWave components and systems that has, in turn, created a need for cost effective test and measurement solutions for high frequency applications. A large number of test instruments are already available in the field as well as new developments coming on-stream for engineers to choose from, ranging from signal generators and spectrum analyzers to network and noise figure analyzers.
Farran Technology supplies frequency extension modules for vector network analyzer (VNA) applications in a range of 40 to 325 GHz that are external to the VNA instruments. With the increased interest in 60 GHz communication links, the company has developed a new range of frequency extension products designed specifically to meet the needs of customers involved in this growing mmWave test area.
mmWave applications correlate closely with how such signals propagate in the atmosphere. The frequencies for which atmospheric attenuation is low (44, 86, 94, 140 GHz) are particularly useful in communication systems operating at long ranges, such as satellite communications, backhaul mmWave radios and point to multi-point radio links. For short range communications, the 60 GHz band provides enough range where only a local area, short distance transmission is required.
During the last decade, substantial knowledge about the 60 GHz mmWave channel has been accumulated and different architectures have been analyzed to develop new mmWave communication systems for commercial applications. Due to the large propagation and penetration losses, 60 GHz wireless local area networks (WLAN) are primarily intended for use in short-range and single room environments. Moreover, demands for high speed multimedia data communications, such as huge data file transmission and real-time video streaming, are markedly increasing.
Hence, one of the most promising solutions to achieve a gigabit class wireless link is to use mmWaves for the carrier frequency. Many system proposals under the IEEE 802.15.3c task group for wireless local personal networks (WPAN) have been studied. The assignment of a large unlicensed bandwidth (~8 GHz) around 60 GHz created new opportunities for 60 GHz front-end technology. High frequency and even mmWave analog communication circuits, which were traditionally built on more expensive technologies such as bipolar or gallium arsenide (GaAs), are gradually being implemented on CMOS.
Also, recent progress in electronic devices has opened the way to operate at data rates up to several Gbps. Quadrature amplitude modulation (QAM) is widely used for the high-speed data transmission. Compared with other digital modulation techniques like phase shift keying (PSK) or pulse-amplitude modulation (PAM), QAM modulation has better anti-noise performance and could make full use of the bandwidth.
COMMUNICATION LINK FREQUENCY EXTENDERS
The S-parameter characterization at RF and microwave frequencies is readily available in most VNAs available on the market today. To extend the range of microwave test systems, frequency extension modules that utilize both multiplier as well as harmonic mixer technologies must be used. mmWave S-parameter measurements are necessary where material characterization, on-wafer measurement and research in communication, imaging and security are of interest.
To this end, Farran Technology offers frequency extension modules for VNA applications that are external to the VNAs. The operation of these modules is based on phase and amplitude up- and down-conversion, which can be applied to all major VNAs. The setup relies on the internal firmware configuration of the VNA which defines RF, LO and IF signal frequencies to and from the extension heads.
The modules effectively multiply the existing RF range capabilities of the network analyzers, enabling measurements to be taken at mmWave frequencies and down-converting the results to the intermediate frequency (IF) that are then supplied back to analyzer for its own RF conditioning and post processing. The front panel of the VNA working at mmWave band reflects the frequency of operation of the device under test (DUT) with no need for further user frequency scaling. That way the analyzer microwave functionality is available at the mmWave range, which includes the setup, calibration and measurements.
With the increased interest in 60 GHz communication links, Farran Technology has developed a new range of frequency extension products designed specifically to meet the needs of customers involved in this growing mmWave test area. This product is an extension of the successful Frequency Extension VNA (FEV) range and the new product family is known as the Frequency Communication Extender (FCE) range.
The FCE-15 system is designed to work with an arbitrary waveform generator in the up-conversion chain and a suitable oscilloscope at the receiver side. The general system architectures are given in Figure 1 and Figure 2. The current up-converter takes an input of an I/Q signal on a 6 GHz carrier but there is also a release that will have an extra stage of up-conversion allowing for direct I/Q signals without the need for the carrier.
The current system demo (see Figure 3) is an example of the system operating in conjunction with the Keysight M8190A arbitrary waveform generator (AWG) and the Keysight DSA series oscilloscope with vector signal analyzer (VSA) software to analyze the signal, which can also be viewed on video: www.microwavejournal.com/60ghzlink. The system takes external LO to allow for the RF signal to be swept across the full 57 to 65 GHz band of interest for 60 GHz communication systems.
The system is designed to produce output power at 1 dB compression (P1dB) of +20 dBm from the transmitter and a receiver noise figure of less than 10 dB (~ 7 dB typical), thus giving excellent dynamic range within the system. The up- and down-conversion gains can be adjusted to suit system architecture (optimal IF input and output levels, etc.). The system also incorporates dual conversion in the up-converter chain to allow for unwanted sideband filtering. Individual converters can be used as references (or “golden radios”) for transmitter or receiver testing, or the combination can be used for antenna or component testing.